The prior art has traditionally delivered topically effective pharmaceutical agents in creams, lotions and gels, all of which require the user to soil his fingers and hands in the application of such medicaments and in the subsequent action of "rubbing it in". Further, such products are greasy, slow to dry and inevitably leave a residue which not only is visible, but rubs off onto clothing and the like, all of which are discomforting to the social ease of the user and may damage clothing through the bleaching action of benzoyl peroxide.
One variation from the traditional creams, lotions and gels occurred with the development of the so-called stick delivery systems which were used to apply anti-perspirants, deoderants, lip balm, lip coloring and like ingredients which are generally applied to the surface of the skin.
Antiperspirant sticks based on the combination of a volatile silicone, a fatty alcohol and a powdered antiperspirant were recently developed and marketed. These sticks, however, have not been extended beyond simple antiperspirant sticks using water soluble inorganic antiperspirant salts. This limited use is the result of the known mechanism of antiperspirant vehicles and the need to intentionally design such delivery systems so as to limit the amount of active ingredient (antiperspirant) which can penetrate into the skin. For an antiperspirant to be efficacious, a large concentration of the active ingredient must be maintained on the surface of the skin from whence it is slowly dissolved and diffused into the apocrine ducts, rather than being absorbed through the skin. To extend this prior art to other pharmacologically active topical agents, it is necessary to greatly enhance the amount of the drug which is able to penetrate through the skin to reach the desired sites of action. This absorption of a drug through the skin is referred to as percutaneous absorption.
Nor does the typical lip balm formulation solve the problem because such products normally contain large amounts of wax (such as Beeswax, Carnauba, and the like), and oils, (such as, castor oil, lanolin and the like), whereupon a greasy/oily sensation is created on the skin which is not only unpleasant but gives the user the feeling of being "dirty". In addition, this type of formulation, as with antiperspirants, severely limits the percutaneous absorption of most drugs through the skin.
Likewise, the conventional creams and lotions fail to obviate the problems enumerated because the creams and lotions are excessively greasy and have the potential to sequester the active ingredient so that the percutaneous absorption of the drug and its efficacy is reduced.